First principles calculations were performed to study the hardness, electronic and elastic properties of lanthanide nitrides in rocksalt structure. The calculated lattice parameters are in good agreement with experimental and other theoretical values. The calculations indicate that NdN, PmN, SmN, EuN, TbN are mechanically unstable. The lower BIG and Poisson's ratio of HoN and ErN show that they are brittle than other lanthanide nitrides. Results reveal that the ligand field stabilization energy and lanthanide contraction play important roles in determining the hardness of lanthanide nitrides in rocksalt structure. (C) 2009 Elsevier B.V. All rights reserved.